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THERE ARE 13 OF THEM AND NOT 12.
YOU CAN SAY ALL OF THEM IF YOU COMPARE THE RULES OUTLINE WITH WHAT ORACLE HAS TO OFFER.
BUT OFCOURSE IT'S A BROADBASED QUESTION.
YOU CAN DEBATE FOR HOURS ON THE INTERPRETATIONS OF ORACLE THAT ENHANCE IT'S SCALABILITY BY INNOVATIVE ENHANCEMENTS TO THE SQL WHETHER THEY GO OFFTANGENTS OR COMPLY THRU AND THRU WITH THE RULES.

Nonsubversion Rule:There should be no way to modify the database structure other than through the multiple row database language (like SQL).

"Nonsubversion rule" is of not much significance in today's world. Most databases today support administrative tools that allow some direct manipulation of the datastructure.
Many people may find the DBA tools faster and easier than command language (SQL).
I think the Codd rules should be taken as guide lines and not standard.
But.. true.. it can be debated for hours without any conclusion !!

The rules are 12, not 13. You probably have heard of Rule Zero and that is why you think the rules are 13.

"For any system that is claimed to be a relational database management system, that system must be able to manage data entirely through its relational capabilities."

If you check Codd’s 12 rules and apply them in a way that you give 1 point if the DB fulfils the rule, 1/2 point if the DB fulfils the rule partially and 0 point otherwise, then Oracle 8 is top on the market with 8.5 points.

"Nonsubversion rule" is of not much significance in today's world. Most databases today support administrative tools that allow some direct manipulation of the datastructure.
Many people may find the DBA tools faster and easier than command language (SQL).
I think the Codd rules should be taken as guide lines and not standard.

Codd did not ask you to use SQL. If we mortals have made an imperfect language to access the database, that does not mean that the rule itself is flawed.